Thermal cut-out or fuse.



UNITED STATEs PATENT OFFICE.

OTT() FEUERLEIN,AVOF CIIARLOTTENIURG, GERBAY, ASSIGNOR T0 TIIE SIEMENS da IIALSKE ELECTRIC CQMPANY, FVCHICAGO, ILLINOIS.

THERMAL 'cuT-ou'r on FUSE.

SPECIFICATION forming part of Letters Patent No. 663,24i, dated November 6, 1900. Application filed September 9, 1899. Serial No. 7 29,897 KNO model-l To a/ZZ whom it may concern.-

Be'it known that I, OTTO FEUERLEIN, a sub ject of -tlie Emperor of Germany, residing at Charlottenburg, Germany, have invented a certain new and useful Improvement in Ther mal Cut-Outs or Fuses, (Case No. 237,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification. y

My invention relates to thermal cut-outs or fuses, and has for its object theprovision of means whereby itis possible to ascertain the physical condition of a concealed or inclosed fuse. l

Where safety-fuses are wholly surrounded by insulating material orare otherwise concealed, itfrequently is difficultto ascertain by inspection thereof whetheror not the fuse is intact. Especially is this the case when the fuse is burned as the result of a protracted heavy overload instead of a violent short circuit, since under the former circumstances no marked disturbance at the fuse results, 'In such a case the circuit would be opened without warning. To overcome this difficulty, I provide a small accessible supplemental test-wireconnected parallel with the main fuse wire or strip. In practice I preferably include both wires in the same inclosure, but separatethe same by an insulating-wall. The supplemental wire is visible from the exterior of the inclosure.

I will explain my invention more particularl y by reference to the accompanying drawings, in which Figure 1` represents a longitudinal crosssection through a fuse device constructed in accordance with the invention, its association with a circuit being indicated diagrammatically. Fig. 2 is a vertical cross-section on line 2 2 of Fig. 1.

Like letters of reference indicate like parts in both views,

A cylindrical box a is preferably made of suitable insulating material and is divided into two compartments of unequal size by an insulating-wall b. The smaller chamber or compartment may be provided with an opening c. 'lhc main lfuse portion being larger d and translating devices or means d2.

is disposed and concealed w-ithin the larger chamber. The fuse d is provided with any suitable terminal portions or strips e, which serve to include the fuse in the circuit to be protected. These plates may also serve to seal the fuse-chamber. The fuse (lis shown connected in circuit with a source of current The auxiliarywire or fuse portion f is also connected with the terminal strips or portions e e, whereby the fuse portions d and fare connected in parallel. Upon the burning of fuse d the auxiliary fuse also burns. As this wire f has relatively a much larger radi-atingsurface than the fuse d, however, it will not ,heat so quickly, and hence will melt later than the fuse d. The wirefmay also be construct-ed of a more refractory material than the fuse d, the object being to provide a supplemental fuse that will melt after the main fuse.

I am aware that it is old to provide main and supplemental fuses in parallel relation with each other and to arrange the supplemental `fuse so that it vmay be seen from the exterior of a single inclosure containingboth fuses, these fuses being designed to burn at the same time. The difficulty, however, with fuses of this character of the prior art lay in the fact that there was no absolute provision made for preventing the auxiliary fuse from melting before the main fuse. The auxiliary or supplemental fuses were liable to burn before the main fuses, and, in fact, the premature burning of supplemental fuses was not always likely to be followed by the burning of the main fuses, so that the function of the auxiliary or supplemental fuse would sometimes not be performed. In accordance with my invention the supplemental fuse is of such a nature that it cannot possibly burn before the' main fuse or at the same time therewith; but it must burn after the main fuse,so that if the supplementalfuse is burned it is positively known that the main fu'se is also burned. I accomplish this result by so constructing the supplemental fuse that an abnormal flow of current in the protected circuit that will canse a rupture of the main fuse when divided between the same and the sup- IOO it ie evident departures plelnentel fuse would not cause e rnpture of the supplemental fuse if the path closed by the main fuse were left intact, or, in other Words, the saine proportion of this abnormnl current'initially iiowing through the supplemental fuse would not in itself be suicient to burn the seine, the said supplemental fuse'not being burned until the mein fuse is burned.

As the supplemental fuse j" must melt if the mein fuse hee burned, it is evident that "by simply examining the eniiilinry or supplemental fuse one ie enabled tojufige correctlgT of the coniiition of the mein fuse ci.

i do not wien to be limited to tine location oi' tine supplemental i'nee in en incloeeci ceeing, ne it mey be locnted elsewhere end eecuije the ennie resuli.

lliiileLT-lnni-'e herein eliown and periiculnrly deecriioet= ene embodiment ci the invention, may reezliiy be mede tiier @from without iepnrting from the epirit thence@ en@ ll therefore (le not wish to ice' iiuiitee; tn tine nreciee feeinree eiiownbut. 9

Hering @line described my invention, i cieim new anni decine te secure ley Lettere Pntent ,v

i. The corccinnticn with the mein enpplemenei insee3 of e casing "crining the welle ci hollow strneture, anni ini/inge petition dividing ite interior inte two chambers, the mein fuse beingecntnined in one cinnnileer and Supplementen inse in the other, the seid fuses beine: included in p'ciieliei reietion with een other the circuit, and che chamber the enpplernentei device being; constructed so as to pei-init the letter to be seen, substantially ne described.

2. The combination with the main nud suppiemental fuses, of an inclosed casing conteining the fueee, e. partition forming e part off' tllecasing and arranged between the two v insee, the enici insee being included in parnllei relation with each other, :md the casing being constructed e0 es to permit the supplernen'fii fune to Toe eeen, substantially ne deecigibed. p

3. 'Ehe combination with the mein and the supplemental fuses, of a' cylindric casing iinvf ing cloeeri ende, end nleolieving e longitudinally-extending partition dividing itiniotwo longitudinal chambers, the mein fuse being arranged longitudinally in one of tlieee einen@ leere and the enppleineniel fuse in the other, and the casing ieing provided with nu iper- 'ture opening into the chnniner containing 'the Supplemental Elise, wherebytlie letter cnn be neen from cizteide the casing, end n pani-,of terminal stripe, one arranged et euch end of the casing and @zich connected with tlieeuds of tine fuses terminfiting; nt the end of the ceeinp; et which it ie situnteti, the seid ternii- 

